Greenhouse Footer Pour

10.5 cu-yd ST Griswold Concrete Truck Arrives 2008-10-15 at 10:00 am
5 cu-yd, 3,000lb, 5″ slump, 10% overage
For the past month we’ve been working on building a greenhouse which will double as an open shed for winter pig housing, winter farrowing and winter weaning space. We farrow our pig herd year round because we need piglets born in each month so we can both sell spring piglets when the demand is high and sell pork to area restaurants and stores every week of the year.

Above I’m dropping a 2,000 lb boulder from 8′ up to crack the ledge so I can then easily remove it. Don’t try this at home without adult supervision. It’s a D-I-Y pile driver and should be done most carefully. As I drop the rock, I backup and I do it such that the tractor is going uphill from the impact site.
The warm seasons are easy, compared with winter. Year round outdoor pig raising is a little bit unique. There isn’t a book to tell us how to do it. I don’t want to raise pigs in enclosed barns, even in the depth of winter. They are healthier, and we are, if they have access to the outdoors and plenty of fresh air. Pigs are very hardy so the cold is not actually the issue.

Digging the terrace for the greenhouse we moved 440 cubic yards of dirt as well as a lot of boulders. The dug out dirt became a shelf extending the terrace where hay will be stored for the winter. The digging took 40 hours with our half cubic yard bucket on the tractor. Compare this with a JD320 excavator which we had hired earlier this summer to do a little bit bigger terrace that involved about 10 times as much dirt moving which he accomplished in eight hours at the rate of $150 per hour. The excavator cost about 27¢/cu-yd once he was already here to do other work.
Over the past five years we’ve been experimenting with various ways to winter our pigs outdoors. The big key is protection from the wind, protection from wet and plenty of hay. In addition to sleeping snuggled down in the hay in the cold months the pigs also eat the hay – it acts as a winter replacement for the pasture that makes up most of their diet in the warmer months. We discovered that they eat hay quite by accident – they were eating our sheep’s winter hay.

The dirt we moved out of the construction site to make the terrace was filled with boulders. A trick is to dump along the back side of the pile. The boulders then self-sort rolling out to the bottom where I was able to collect them into piles for future stone wall building. This left sifted sand in the piles.
To provide the shelter from the wind we’ve tried a variety of structures each of which has had positive and negative aspects:

• A Pole Shed was our first construction project for the animals. We built it post and beam fashion using tops of trees from our logging. I had only meant for it to last a few years but it’s eight years old now and still going strong. This works well for small to medium sized pigs but isn’t good for the very big pigs in the breeding herd because they chew on the wood and could potentially knock it down because they’re so massive. They love to rub up against the posts.
• Dens dug into the hill work quite well and were our second pig housing for winters. I really like this as they are low into the hill, earth sheltered and very protected from the wind. The roofs were very inexpensive – we made them with scrap metal laid on saplings. The problem is the pigs continued to excavate during the winters. After three years they have extended the dens beyond the back of the roofs.
• Hay Bale Housing works well for a winter season but quickly rots in the spring. The hay must be protected or the pigs tear it down and eat it.
• Ferro Cement Dens work great, are rugged and last. The disadvantage is they’re dark and take a lot of work to build. We have built two and I plan to build more. The second one we built was actually a model of techniques for our cottage.
• Pallet Sheds have served us well. They’re not suitable for the very big pigs in the breeding herd, just like the pole shed although they’re great for weaners, growers and finishers. We have used them for farrowing spaces. The pallet sheds are very temporary in their nature because the wood in contact with the ground rots out eventually.
• Greenhouses made of 661010 Welded Wire Mesh (WWM) are great. They’re lightweight, can be easily moved and provide a wonderful, warm winter environment. This also works for chickens. The disadvantage is they’re lightweight, can be easily moved by the pigs and the wires and plastic get torn. A solution is putting them up onto knee walls above the reach of the pigs. Wooden knee walls rot out and get abused by the pigs but stone or concrete works great.
• A Glazed Shed roof like the south end shed worked very well but since I intend to remove the old farm house I don’t want to keep adding sheds to the sides of it.
• Other Things we’ve considered are old shipping containers (difficult to get on site & metal which will rust out), hoop greenhouses (would be trashed by pigs unless on knee walls and then there’s the issue of the covering plastic plus wind), plastic porta-huts (break in our extreme cold, too small, don’t last and too expensive) and converting the old farm house into a barn (interferes with selling it and it is made of wood).

Bowling Buddies Ben and Hope are collecting rocks to use in the form work. Interestingly, there are very few rocks in the 1″ to 4″ size compared with the volume of dirt and the number of larger rocks.
Looking back over our experiments we decided that the best idea would be something:

• Built into the hillside for shelter from the cold winter winds
• Oriented to protect from the winds and catch the low winter sun.
• Glazed roof for lots of light inside.
• Able to serve as a greenhouse so that plants can help with nutrient export as well as giving us an extended growing season.
• Graded to provide drainage to keep it dry.
• Stone or concrete knee walls as high as the pigs reach so it will be virtually indestructible.
• Open to the outdoors for lots of fresh air – basically a three sided shed.
• Large enough to allow us to use the tractor to deliver large hay bales into it.
• Cleanable with the tractor when necessary.
• Able to serve multiple function as needed by simply dividing up the partitions for:
  • Herd sleeping space in the winter
  • Farrowing winter space
  • Weaners
  • Growers
  • Greenhouse area for plants

The site is not perfectly level. In fact, I purposefully sloped it about 24″ across the 70′ length so that the packed sub-soil will better drain water away from the foundation and interior of the greenhouse. We then picked the highest point and drove a rebar stake in the corner to be our reference. From that we strung tight level strings to additional stakes at the other three corners of the site. Using geomet
ry, a quick lesson for homeschoolers on site, we squared up our stakes and checked that the diagonals using the Pythagorean theorem: h²=a²+b² When you homeschool, the classroom is everywhere.
Eventually we plan to have it such that the greenhouse and the weaner space will be the same by using raised beds in the greenhouse so the weaner pigs can be on the floor below the beds. At that point we’ll subdivide the space into a glazed greenhouse/weaner area with farrowing and herd spaces along the east side.

During the warm months the herd will be back out on distant pastures and the entire structure can be used as a sheltered semi-greenhouse for extending our growing season. The pigs will never be closed in – instead the spaces open out onto sacrificial winter paddocks so the pigs always have access to the outdoors just as we’ve always done. Food and water will continue to be at a walking distance from the greenhouse so that the pigs can’t become couch potatoes in the winter – they’ll have to get their daily walks which is important to their health, helps spread their manure and improves the quality of their meat.

Ben rechecking form levels with a jig stick.
Gettting the forms level is a progressive process. As we work we keep checking that our level line is level and that the forms are level off of the line. It is important to have the level lines stretched very tightly. In reality, due to gravity, they are curves. We want very shallow curves. The maximum angle relative to gravity is found at the ends of the strings so those are the points to check with the line level. Check them both. If you check in the middle area of the line it can be, quite deceptively, level while the line is not level.

Holly Chopping Rebar with the Big Cutters
Actually, she can’t. Even with those huge levers it still takes a lot of force. Despite being a big strong Vooman she needs an assist from Will or I. Nothing to be ashamed of – team work makes the job happen.

Hope Marking Braces
Speaking of team work, here is Hope, age 5, using a ruler to mark the mid-points of the footer cross braces. I then followed her with the drill to make holes for the rebar. The braces serve to hold the footer side board forms at the right spacing, hang the long horizontal rebar so it is up off the ground using wire ties and hold vertical the rebar starter stubs for the walls.

Will Make Forms For Food
Will has been making most of the larger forms for our project. These are 1’x8′, 2’x8′ and 4’x8′ panels consisting of a piece of 1/2″ plywood and stud framing to make it rigid. These reusable forms will get saved after we complete this greenhouse so that we can build more greenhouses and other projects. Making the forms once and using them many times will save a lot of time on future building jobs.

Holly Transporting Forms
Will makes the forms up by the cottage where we have electricity for the skilsaw as well as an easy drop off point for receiving materials. Holly then transported them down to the construction site on the tractor fork lift.

Holly and Hope setting up Forms
In the north east corner we needed 24″ high forms. Rather than building a lot of extra specialized forms we used 4’x8′ forms on their sides – forms we’ll also use for the walls to come. This saved time and construction materials. The forms are put together with sheetrock screws. After leveling with rocks the bottoms are chinked with stones.

Form Level Line
When filling the forms with concrete we need to know how high to go. A pencil mark would get covered with cement. A string would get moved. By putting screws through the wood with their tips poking into the interior of the form we made lines that we could feel with our tools as well as see.

South East Corner Serif Detail
The footer form is shaped like a letter C with serifs to strengthen the ends. The serifs are extra thick because the pigs will love to rub up against them to scratch their sides and, heaven forbid, the tractor might bump into the concrete. Thus the corners must be pig and tractor tough.

North East Corner Serif Detail
Like the other corner, this serif is extra thick. Because it is taller on this end, to get the draining slope, it has the high plywood forms instead of just 2×6’s.

Rebar Overlap
We used 20′ long sections of #4 rebar (1/2) in the footers. They over lap by 18″ and are tied together at the junctions. The rebar gives tensile strength to the footer. The concrete gives compressive strength. Together they make for a strong, long lasting foundation. Rocks were used to fill in gaps below the footer form boards as well as to brace the boards in place.

It is important the rebar be fully encased in the concrete. Exposed rebar can allow water to flow in, rust the iron which expands cracking the concrete. Thus the rebar pieces are hung from the cross braces. In the photo above a sheetrock screw has been used to set the rebar in place.

North West Corner
To give extra strength to the footer the North West and South West corners are expanded to triangles with extra rebar. The taller sheet of plywood is a bounce board to catch dropping cement when it comes shooting out of the chute.

Tall forms like this need steel wire cross ties through the forms and around the 2×4’s down near the ground and part way up to keep the forms from spreading as concrete is poured in. The concrete is very heavy. As it becomes a tall liquid column it exerts a lot of force at the bottom of the form.

chute Parts
To get the concrete from where the truck can manuver to where we need it in the forms we built a chute, a sluiceway. Each section is made of one sheet of 1/2″ plywood cut into three 16″x8′ sections as well as two 8′ long 2×6’s and two 94″ long 2×6’s. The shorter 2×6’s are the joining boards that are sticking out of each section. By being slightly shorter they allow the chute parts to lock together more tightly shoul
d we be off a little in our placement of the boards. 1.5″ and 2.5″ sheetrock screws were used to put the chutes together.

Finished Concrete chute
In addition to the three chute sections pictured above there is one more which does not have the joining boards. That last chute goes on the bottom end and has a hinged openable shutter for catching the concrete so the chute can act as a queue while the tractor is delivering concrete from the chute to distant forms. Stakes along the chute were driven into the ground and then screwed to the chute to lock it in place on the hillside. At the bottom angled brace boards keep the chute from sliding down hill or tipping side to side. The resulting sluice way is rock solid and ready to carry five cubic yards of concrete.

The concrete chute is 32′ long and has a drop of about 4′ giving a slope of about 1 to 8 – in other words a drop of 1.5″ per foot. Using concrete with a slump of 5″ it was reasonably easy to hoe down the chute yet it didn’t overflow out of the chute too fast. This was handy as it allowed the hoe team to build up a store of concrete in the chute ready for the next tractor bucket load while I moved the previous load into the forms.

By the way, a slump of 5″ means that a 12″ cone of concrete will slump downward 5″ to a 7″ pile when the cone is removed. See this post for more discussion of slump and concrete.

Ben Puttying Screw Heads
You’ll notice we kept the concrete chute low to the ground. This makes it easier to hoe the concrete down, easier to build the supports strongly and safer. I would not like to have over 2,000 lbs of concrete loaded chute tip over!

Hope Puttying Screw Heads
There are a lot of tasks that small hands can take on. Here Hope is putting plasticine putty into the screw heads. This keeps them from filling with cement and thus becoming nearly impossible to remove. I learned this little trick from Cheng’s books on making concrete counter tops.

Holly Oiling Forms
After the concrete has cured we’ll want to retrieve our forms. The concrete can stick rather well to the wood, especially if there are rough spots on the wood. To help release it we painted the inside of the forms with oil the morning of the pour.

Concrete Truck chute
Wess had three extra chutes standard on the truck such that he can extend the truck’s chute about 18′. This allowed him to deliver the concrete directly to our chute where we deliver it down to the tractor.

Will, Hope & Ben pushing concrete down the chute.
As the truck delivered the concrete into the top of our chute we pushed it downward to fill the tractor bucket. Once the tractor bucket was filled we closed the end flap and accumulated another batch down near the end ready to dump in the tractor bucket.

Walter Distributing Concrete in Tractor Bucket.
The chute delivers the concrete to one small area in the bucket and then I pulled it across to get an even load for carrying to the far forms.

Tractor Dumping Concrete
Each bucket full of concrete filled about two sections of form work each about six feet long in the low areas. We used a total of ten bucket loads of concrete averaging about 0.45 cu-yds in the 0.5 cu-yd tractor bucket. There was some spillage but not too bad. With the 10% overage I put in we came out exactly at the right amount of concrete.

Will gives hand signals to direct Walter
We use sign language a lot when working due to the noise of the tractor. Some signs are obvious this way or that in addition to American Sign Language (ASL) and custom signs we have in our own dialect. Having clear signs that are well known makes working more efficient, safer and accurate.

Cleaning Tools
We finished up our pour about 12:30 pm. That was just two and a half hours of work for our team of five. With another 15 minutes of cleaning and oiling tools & the bucket we were done and ready for pizza!

Fall Colors – Blue Sky
It was a beautiful day to pour concrete with the fall colors clinging to the hill sides. Today we got a gentle rain that saved us the job of having to keep the concrete moistened. What more could you ask for in a perfect pour?

Pour Day (Weds): Outdoors: 60°F/38°F Sunny
Farm House: 66°F/61°F GH1 Footer poured
Tiny Cottage: 64°F/58°F